The invention relates to a method for monitoring a device that is used to guide an energy source, such as a handling device, for the purpose of applying energy to a work piece (16, 18), which is positioned with the energy source inside a protective chamber that is enclosed by a protective wall, wherein the energy source is moved at a speed V and the speed V of the moved energy source is established as the current speed Vakt.
According to the current state of the art, handling devices for guiding energy sources in the form of laser sources that are used to machine work pieces are housed within a protective laser cabinet, to exclude any possible danger to personnel and neighboring technical systems by laser beams.
It is possible, however, for errors to occur in which a laser that is guided using a handling device may direct the laser beam at a single point or at very low speed toward an outer wall of the protective laser cabinet, so that the outer wall could become destroyed by the energy applied to it. The escaping laser light could then become a hazard to personnel and objects.
For this reason, it has already been provided that the walls of protective laser cabinets are designed to be actively gauging or multiple-shell, or of sufficient thickness, however these measures are highly cost-intensive.
Also known is a process by which an industrial robot is used to guide a gas flame along a plastic component, in order to alter its material properties. In this process it must be ensured that the component does not begin to burn.
In state-of-the-art monitoring methods it is further proposed that the handling device should actuate a preferably dual-channel monitoring switch at fixed time intervals, in order to enable an indirect monitoring of the motion control of the handling device. In this, the system will be switched off if the monitoring switch is not actuated within a firmly established window of time. This means that in the case of error, at the latest following the established monitoring time, the system, including the laser power, will be switched off. In this way it can be ensured that only a limited quantity of energy from the laser source can be applied to a point, for example on the wall of the protective laser cabinet.
To avoid having to interrupt a running production cycle in the device when the monitoring switch is actuated, the monitoring interval must be designed such that even in the most unfavorable case it is longer than the production cycle. But the cycle times for machining a component in a protective laser cabinet can easily range from 30 to 90 sec. Thus the quantities of energy that the laser beam would apply to a single point in the case of error are already so high that quite considerable wall thicknesses for the protective laser cabinet are necessary in order to prevent a breach of the cabinet wall with adequate certainty. For this reason, these alternative methods can be used only conditionally or at substantial cost.
From DE 100 40 920 A1, a process control for material machining using lasers is known. To cause an especially hand-guided machining head to automatically react to changing process parameters without motor-driven axles being absolutely necessary for processing a work piece, a speed-power control is provided in the machining head, whereby the power emitted by the laser is adjusted to the speed of the machining head.
From EP 0 743 130 A1 a control of a laser beam for machining a work piece is known.